Flex Plate?
tci/b&m do not make a 5.9 magnum to 904 flexplate . Use the stock one or have the weights for the magnum welded on to the converter....The 5.9 magnum external balance is different from the LA 360.
there is a web site from a member here that covers the flexplate issue with the Magnum.......
Dodge Magnum 5.9 Flexplate
Automatic Transmission Details
got to love google